1. Field of the Invention
The present invention is directed to the field of optical inspection of web materials and is ideally suited for use in high production facilities where the quality of such materials is of critical importance.
2. Description of the Prior Art
In the textile industry, the quality and use of woven and non-woven material depends upon many factors which occur during the manufacture and handling of the fabric. One measure of quality is the number of fabric elements per unit length of material. In woven material, the number of warp threads per unit length is generally held constant by monitoring devices at the weaving loom. However, the number of fill threads per unit length is critical in first quality goods for particular uses and tends to vary due to tension changes that occur during the weaving operation or improper yarn size. The concentration of fill threads is generally determined in the industry by periodically sampling a small length of material and manually counting the number of fill threads. Needless to say, this is laborious, as well as time consuming and does not allow for even the hope of performing 100% inspection of the woven product.
Several automatic systems have been disclosed which measure the density, the reflectivity and the size of web material as it is transported past an inspection point. However, the measurement of the number of fabric elements per unit length continues to be performed manually.